1. Field of the Invention
This invention relates generally to data encoded on storage media and relates more particularly to a system and method for correcting interference errors in data encoded on storage media.
2. Description of the Background Art
Efficient, economic, and reliable storage of digital data is an important consideration of manufacturers, designers, and users of computing systems. In magneto-optical storage devices, digital data is typically stored in tracks located on rotating disks of magneto-optical (MO) storage media. Close positioning of the adjacent disk tracks maximizes the amount of stored magnetic data on a storage disk, thus providing significant economic benefits to system manufacturers and users. Therefore, system designers frequently seek new and improved methods of reducing track pitch to permit greater storage capacity on the storage media.
Storage devices using magnetic super resolution (MSR) storage media allow for very narrow track pitch. A MSR media produces a readout aperture when heated by a light spot. The aperture allows magnetic data in a storage layer to become visible. The edges of the aperture mask magnetic data stored in adjacent tracks, so there are typically negligible interference errors in the magnetic data read from the MSR media.
In MO storage devices, magnetic data is typically stored and retrieved from the storage media using a magneto-optical head. The head must be accurately positioned above a selected track while storing or retrieving data. One method for position correction of the head utilizes read-only data encoded on a surface of the storage media. This type of data is read by detecting a change in amplitude of a light signal reflected from the surface of the storage media, instead of by detecting a magnetic field in the storage layer. There is no masking effect for read-only data, so when the track pitch is narrow errors due to adjacent track interference may occur.
Errors in the read-only data may cause the head to be positioned incorrectly, which in turn may cause the MO storage device to perform unreliably. Therefore an improved system and method are needed to correct interference errors in data encoded on storage media.
In accordance with the present invention, a system and method are disclosed to correct interference errors in data encoded on storage media. The invention includes position marks disposed on a storage medium, the position marks being configured to encode a plurality of track addresses and to encode track types. A correction module detects and corrects errors in the track addresses by combining each of the track addresses with one of the track types so that the track type becomes part of the track address. The correction module then recognizes incorrect addresses, and replaces the incorrect addresses with correct addresses. Each incorrect address is not identical to a correct address.
In one embodiment, the position marks encode at least four track types, and each track address includes a high-order address byte and a low-order address byte. The low-order address bytes are encoded in track pairs, so the address and one of the track types uniquely identify each track. Each low-order address byte contains a check bit used to correct single bit errors in each corresponding high-order.byte. The position marks that encode the track types are also used to generate a position error signal for position correction of a head device used to store and retrieve data from the storage media.
Therefore, the present invention more efficiently and effectively corrects interference errors in data encoded on storage media.